The present disclosure relates generally to light emitting diode (LED) devices, and more particularly, to an LED lighting device with thermoelectric module.
LEDs are used in solid state lighting devices as electric light sources. Compared with traditional light sources, such as incandescent and fluorescent light bulbs, they have many advantages, such as lower power consumption and much longer life (e.g., about 50,000 hours). These advantages are only possible, however, if the device is kept cool. The high power LEDs being utilized and promoted for use in today's lighting markets all require heat sinks in order to maintain the LED at temperature that is sufficiently low to give it long life and maintain its brightness.
Traditional incandescent and fluorescent light bulbs have approximately 80% waste heat and radiate the heat out of the light bulb, while LEDs, have approximately 20% or less waste heat but dissipate it by heat conduction out the back of the device. Thus, traditional light sources do not require a heat sink since the heat is radiated out and the internal components are not heat sensitive; whereas, LED light sources require a heat sink since the heat needs to be conducted out of the LED device and the devices are heat sensitive.
LED lighting devices generate critical thermal energy which, if not removed, may prevent proper functioning of the device or limit the lifetime of the device. FIG. 1 illustrates an exemplary LED lighting device employing a heat sink/housing in thermal communication with the LED element so as to provide cooling by dissipating heat into the ambient air.
FIG. 1 shows an exemplary LED lighting device 10 having a heat sink housing 12. The housing 12 may be formed of a thermally conductive material, such as a metal or metal alloy or a thermally conductive polymer material. A lens covering (not shown) may be provided over the open end of the housing 12.
One or more LED light elements 16 (one in the depicted embodiment) are mounted on an LED circuit board 18, which is mounted within the interior cavity defined by the housing 12. A heat slug 28 is adjacent and contacting the LED element 16. The heat slug 28 is in thermal communication with an adjacent portion 22 of the housing 12 (for example, via a thermally conductive vias (not shown) in the circuit board 18, a heat spreader plate or other conductive member (not shown) intermediate the circuit board 18 and the adjacent portion 22 of the heat sink/housing 12, etc.
When the LED device 10 is on, the LED light 16 generates heat and the heat slug 28 conducts the heat through the LED circuit board 18 to the housing 12, which acts as a heat sink to dissipate the heat into the surrounding air. A series of fins 30 may be provided on the heat sink/housing 12 to increase the surface area of the air/housing surface interface and thus facilitate heat dissipation.
The present invention uses a thermoelectric module to recover some of the energy associated with the heat generated by the LED element 16 rather than dissipating it as waste.
A thermoelectric cooler, sometimes called a thermoelectric module, thermocouple, or Peltier device, is a semiconductor-based electronic component that functions as a small heat pump. Alternatively, metallic thermoelectric modules having a junction of dissimilar metals are also known. There are also new thermoelectric modules based on nano and bio technologies that are currently in development that could be used as well. There may be the development of injection molded thermoelectric modules that use a combination of dissimilar fillers or metals that provide for a thermoelectric effect when combined in a molded part. By applying a low voltage DC power source to a thermoelectric module, heat will be moved through the module from one side to the other. One module face becomes cold while the opposite face simultaneously becomes hot. It is important to note that this phenomenon may be reversed whereby a change in the polarity (plus and minus) of the applied DC voltage will cause heat to be moved in the opposite direction. Consequently, a thermoelectric module may be used for both heating and cooling thereby making it highly suitable for precise temperature control applications.
Conversely, thermoelectric materials can convert thermal energy directly into electricity. By applying a constant heat source to one side to make it hot (the heated side) and a heat sink to the other side to keep it cool (the cold side) a temperature difference can be created and maintained. When this happens, the thermoelectric module will convert the temperature difference into electricity. This effect is the Seebeck effect.
Thermoelectric coolers are currently used to harness energy and convert that energy to electricity for applications where there is a tremendous amount of excess heat generated, e.g., geothermal energy, power plants, and generators.
In addition, thermoelectric coolers are used as generators to power wireless sensors. Thermoelectric cooler devices can be attached to a heat source such as a hot water pipe. The thermoelectric cooler also has a heat sink with a wireless sensor attached. As the heat passes from the heat source to the thermoelectric module, the heat sink keeps the heat sink side of the thermoelectric module cooler than the heat source side, resulting in a temperature difference which is converted into electricity to power the wireless sensor.
As a result of the lower power consumption and longer life of LEDs, compared to traditional light sources, today's lighting market and governments worldwide are utilizing and promoting use of high power LEDs. With government and market support, LEDs are gaining wide acceptance and adoption into mainstream lighting applications. As the global lighting requirements are continuously growing, LEDs are enabling emerging markets and under developed areas to have light sources because of the low power consumption and ability for LEDs to be powered by solar energy.
The present disclosure contemplates a new and improved LED lighting device, which includes a thermoelectric module for converting waste heat from the LED light elements into electricity.